1. Field of the Invention
The present invention relates generally to medical diagnostic devices and methods. More particularly, the invention discloses methods and devices for characterization of a hollow organ by moving a balloon-tipped catheter through an internal lumen of such organ. Tissue elasticity, compliance, or distensibility distribution along the lumen as well as its diameter variations are some examples of what can be measured using the present invention.
A physiologic function of many organs and systems in the body depends on their mechanical and geometrical properties. Gastrointestinal tract, urinary tract, breathing and reproductive systems as well as blood vessels and the circulatory system in general are just some examples of physiological systems containing hollow organs and lumens that may need such characterization. The following description provides some examples in which using the present invention may be advantageous.
Gastrointestinal tract. Biomechanical properties of the large and small intestine in-vivo are largely unknown, despite the fact that their distensibility is important for normal function, and altered mechanical properties are associated with gastrointestinal (GI) diseases. Data in the literature pertaining to mechanical aspects of GI function are concerned with the contraction patterns, the length-tension relationship in circular and longitudinal tissue strips in vitro, flow patterns, the compliance and the stress-strain relationship. Traditionally used methods for clinical or basic investigations of the GI tract are endoscopy, manometry and radiographic examinations. Although these methods provide useful diagnostic information, they do not assess tissue biomechanical parameters which could be important for characterization of the state and functionality of the organ.
Obstructive diseases of the rectosigmoid region including anorectal canal and rectum may include various growths and polyps that impact the wall elasticity of these organs. Both passive and active evaluations of this region (active evaluation describes the evaluation in the presence of conscious or involuntary muscle contraction) may allow for diagnosis and management of the anal incontinence and other diseases.
Proper catheter-based minimally invasive tools are needed to allow mechanical compliance characterization of various sections of the GI tract.
Lower esophagus. Studying the gastroesophageal junction and in particular the lower esophageal sphincter is often necessary to diagnose various esophageal disorders such as gastroesophageal reflux disease, stricture, achalasia, diffuse esophageal spasm, esophageal cancer and dysphagia. These esophageal disorders affect the ability of the sphincter to open and close normally. The sphincter rests in a closed position to shut off the end of the esophagus, and is relaxed when in the open state. However, the sphincter does not have the ability to open on its own; rather it opens briefly by normal physiological function of the esophagus during excitation of the inhibitory nerves of the esophagus. New methods and devices are needed for comprehensive characterization of the elasticity of the lower esophagus and the sphincter in order to diagnose its various anomalies and diseases.
Urinary tract. Many organs and lumens of the male and female urinary system are in need of mechanical characterization. Urethral and prostate mechanical properties in men play a critical role in the diagnosis and management of prostate enlargements, both benign and malignant. Prostate enlargement affects the stiffness and elasticity of the urinary tract in its vicinity. Evaluation of the urinary tract compliance allows for indirect and minimally invasive diagnosis of prostate enlargement.
Male and female urge and stress incontinence involve various portions of the bladder and lower urinary tract organs. While urodynamics evaluations allow for diagnosis of many aspects of these conditions, elasticity of the urinary tract organs have not been studied to a degree allowing its inclusion in the standard series of tests for patients with incontinence complaints.
Reproductive system. The cervix is the lower portion of the uterus. It is composed of fibrous tissue and its mechanical integrity is crucial for maintaining a healthy gestation. During normal pregnancy, the cervical extracellular matrix remodels in preparation for labor. To date no diagnostic tool is yet available to objectively assess the in-vivo biomechanical properties of the uterine cervix during gestation in order to objectively detect or confirm the onset of cervical insufficiency or premature labor leading to a preterm birth of a baby.
Circulatory system. Atherosclerosis is a global disease affecting both coronary as well as peripheral blood vessels. Sophisticated imaging techniques have been developed in recent years allowing characterization of blood vessels and detecting of anomalies associated with plaque deposits on their walls. Development of comprehensive examination methods for compliance assessment of blood vessels will further improve diagnostic accuracy and clinical decision making as to proper intervention when plaque deposits are identified.
In addition to plaque deposits, various other diseases cause flow restriction throughout the circulatory system, such as aortic stenosis or vascular spasms. Compliance evaluation of various blood vessels will open new opportunities for diagnosis and management of various cardiovascular diseases.
Elasticity assessment tools and methods of the prior art involve generally a catheter or a tube equipped with a single or a series of inflatable balloons. The catheter is placed in the lumen of a hollow organ or vessel and balloons are inflated to push against the wall of the lumen. Pressure-volume curve is then created characterizing the wall of the lumen and its surrounding organs at that location. This general approach works well for spot-checking of elasticity. However, many diseases are extended throughout the length of the lumen and therefore are not amenable for evaluation using these devices.
2. Description of the Background Art
Numerous patents and patent application describe use of inflatable tools inserted in a hollow organ of the human body in order to obtain the mechanical response from the surrounding tissues and to estimate their mechanical, geometrical and functional characteristics. A cuff inflatable by air combined with a pressure gauge was proposed for monitoring sphincter type muscles (U.S. Pat. No. 4,776,347). Multiple pressure sensors with a stimulus balloon were aimed to measure muscle activity in the anorectal canal (U.S. Pat. No. 5,924,984). Disposable infusion balloon-tipped catheters in connection with pressure monitoring sensors were proposed for measurements of physiological pressure in the urinary system (U.S. Pat. No. 6,447,462) and for estimations of particular pressure, internal cross-section and diameter of blood vessels basing on the balloon fluid pressure (U.S. Pat. No. 5,275,169). Pressure-volume and force-deformation relationships of inflatable balloons can be used for calculation of morphometric parameters of hollow organs, such as the wall thickness (US Pat. Appl. 2008/0027358), active and passive elastic properties of muscle walls (US Pat. Appl. 2005/0124920), urinary incontinence parameters (US Pat. Appl. 2002/0111586), biomechanical parameters of esophagus (US Pat. Appl. 2007/0015994), etc.
The present invention is aimed at significant innovative enrichment of the methods of measuring structural and biomechanical parameters of hollow organs using inflatable balloons and relationship between pressure-volume increments by introducing axial profiles of elasticity built on the basis of a plurality of records along the examined organ at different levels of straining.